The invention relates to pyrotechnic caps and particularly to hermetically-sealed pyrotechnic caps capable of being activated by radiant energy in the form of light and/or heat.
In the aforementioned U.S. Pat. No. 4,103,082, there is described a unique concept in the production of substantially simultaneous, high intensity audible and visual signals. As described in U.S. Pat. No. 4,130,082, it has been discovered that hermetically sealed plastic caps having a pyrotechnic composition therein can be instantaneously activated by the highly intense light and/or heat from an adjacent flashlamp to produce an audible signal also of high intensity (e.g. approaching 165 decibels). The preferred activating flashlamps are those presently utilized in the photoflash products manufactured and sold by the assignee of the instant invention under the name MAGICUBE. As also described in U.S. Pat. No. 4,130,082, it is possible to activate the sealed caps using other varieties of flashlamps such as those which are electrically activated. One example of this latter type are the flashlamps currently utilized in the photoflash products manufactured and sold by the assignee of the instant invention under the name FLIP-FLASH.
A primary use for the device in U.S. Pat. No. 4,120,082 is an intrusion alarm. The device may also comprise part of an alarm system wherein a suitable detector is used to receive the device's output and thereafter perform an auxillary function (e.g. emit a prolonged, high intensity signal). Quite understandably, devices such as alarm systems must possess a high degree of reliability. Accordingly, it is essential that the cap member which comprises an integral part of the device must also possess a similar functioning capability.
It has been determined that the presence of moisture within the cap, even in relatively minor quantities, can adversely affect both the cap's reliability and the loudness of the emitted audible signal. This moisture may enter the cap either during manufacture thereof or subsequent to said manufacture by penetration of a defective seal.
It is also known that water vapor is capable of permeating the polymeric side walls of the cap's container upon prolonged exposure of the cap to extreme conditions of high temperature and humidity.
It is believed, therefore, that a pyrotechnic cap member capable of compensating for the presence of moisture therein to thereby assure that the required functional reliability and loudness characteristics of said member will be maintained would constitute a significant advancement in the art.